The betulinic acid derivative IC9564 is a potent anti-human immunodeficiency virus (anti-HIV) compound that can inhibit both HIV primary isolates and laboratory-adapted strains. However, this compound did not affect the replication of simian immunodeficiency virus and respiratory syncytial virus. Results from a syncytium formation assay indicated that IC9564 blocked HIV type 1 (HIV-1) envelope-mediated membrane fusion. Analysis of a chimeric virus derived from exchanging envelope regions between IC9564-sensitive and IC9564-resistant viruses indicated that regions within gp120 and the N-terminal 25 amino acids (fusion domain) of gp41 are key determinants for the drug sensitivity. By developing a drug-resistant mutant from the NL4-3 virus, two mutations were found within the gp120 region and one was found within the gp41 region. The mutations are G237R and R252K in gp120 and R533A in the fusion domain of gp41. The mutations were reintroduced into the NL4-3 envelope and analyzed for their role in IC9564 resistance. Both of the gp120 mutations contributed to the drug sensitivity. On the contrary, the gp41 mutation (R533A) did not appear to affect the IC9564 sensitivity. These results suggest that HIV-1 gp120 plays a key role in the anti-HIV-1 activity of IC9564.
In a continuing study of potent anti-HIV agents, seventeen 28,30-disubstituted betulinic acid (BA, 1) derivatives, as well as seven novel 3,28-disubstituted BA analogs were designed, synthesized, and evaluated for in vitro antiviral activity. Among them, compound 21 showed an improved solubility and equal anti-HIV potency (EC50: 0.09 μM), when compared to HIV entry inhibitors 3b (IC9564) and 4 (A43-D). Using a cyclic secondary amine to form the C-28 amide bond increased the metabolic stability of the derivatives significantly in pooled human liver microsomes. The most potent compounds 47 and 48 displayed potent anti-HIV activity with EC50 values of 0.007 μM and 0.006 μM, respectively. These results are slightly better than that of bevirimat (2), which is currently in Phase IIb clinical trials. Compounds 47 and 48 should serve as attractive promising leads to develop next generation, metabolically stable, 3,28-disubstituted bifunctional HIV-1 inhibitors as clinical trials candidates.
A class of betulinic acid derivatives was synthesized to target two critical steps in the human immunodeficiency virus type 1 (HIV-1) replication cycle, entry and maturation. Each mechanism of HIV-1 inhibition is distinct from clinically available anti-HIV therapeutics. The viral determinants of the antientry and antimaturation activities are the bridging sheet of HIV-1 gp120 and the P24/p2 cleavage site, respectively.
Betulinic acid, a triterpenoid isolated from the methyl alcohol extract of the leaves of Syzigium claviflorum, was found to have a potent inhibitory activity against human immunodeficiency virus type 1 (HIV-1). Betulinic acid derivatives were synthesized to enhance the anti-HIV activity. Among the derivatives, 3-O-(3′,3′-dimethylsuccinyl) betulinic acid, designated YK-FH312, showed the highest activity against HIV-induced cytopathic effects in HIV-1-infected MT-4 cells. To determine the step(s) of HIV replication affected by YK-FH312, a syncytium formation inhibition assay in MOLT-4/HIV-1IIIB and MOLT-4 coculture, a multinuclear-activation-of-galactosidase-indicator (MAGI) assay in MAGI-CCR5 cells, electron microscopic observation, and a time-of-addition assay were performed. In the syncytium formation inhibition assay or in the MAGI assay for de novo infection, the compound did not show inhibitory effects against HIV replication. Conversely, no virions were detected in HIV-1-infected cell cultures treated with YK-FH312 either by electron microscopic observation or by viral yield in the supernatant. In accordance with a p24 enzyme-linked immunosorbent assay of culture supernatant in the time-of-addition assay, YK-FH312 inhibited virus expression in the supernatant when it was added 18 h postinfection. However, Western blot analysis of the cells in the time-of-addition assay revealed that the production of viral proteins in the cells was not inhibited completely by YK-FH312. These results suggest that YK-FH312 might affect the step(s) of virion assembly and/or budding of virions, and this is a novel mechanism of action of an anti-HIV compound.
Betulinic acid derivatives modified at the C28 position are HIV-1entry inhibitors such as compound A43D; however, modified at the C3 position instead of C28 give HIV-1 maturation inhibitor such as bevirimat. Bevirimat exhibited promising pharmacokinetic profiles in clinical trials, but its effectiveness was compromised by the high baseline drug resistance of HIV-1 variants with polymorphism in the putative drug binding site. In an effort to determine whether the viruses with bevirimat resistant polymorphism also altered their sensitivities to the betulinic acid derivatives that inhibit HIV-1 entry, a series of new betulinic acid entry inhibitors were synthesized and tested for their activities against HIV-1 NL4-3 and NL4-3 variants resistant to bevirimat. The results show that the bevirimat resistant viruses were approximately 5- to10-fold more sensitive to three new glutamine ester derivatives (13, 15 and 38) and A43D in an HIV-1 multi-cycle replication assay. In contrast, the wild type NL4-3 and the bevirimat resistant variants were equally sensitive to the HIV-1 RT inhibitor AZT. In addition, these three new compounds markedly improved microsomal stability compared to A43D.
HIV-1; Entry inhibitor; Maturation inhibitor; Betulinic acid; Berivimat; Berivimat-resistance
We previously reported that [[N-[3β-hydroxyl-lup-20(29)-en-28-oyl]-7-aminoheptyl]-carbamoyl]methane (A43D, 4) was a potent HIV-1 entry inhibitor. However, 4 was inactive against HIV-2 virus, suggesting the structural requirements for targeting these two retroviruses are different. In this study, a series of new betulinic acid derivatives were synthesized, and some of them displayed selective anti-HIV-2 activity at nanomolar concentrations. In comparison to compounds with anti-HIV-1 activity, a shorter C-28 side chain is required for optimal anti-HIV-2 activity.
Betulinic acid; HIV-2; HIV-1
Betulinic acid is a natural product possessing abundant and favourable biological activity, including anti-cancer, anti-malarial, anti-inflammatory and anti-HIV properties, while causing minimal toxicity to unaffected cells. The full biological potency of betulinic acid cannot be fully unlocked, however, for a number of reasons, a primary one being its limited solubility in aqueous and biologically pertinent organic media. Aiming to improve the water solubility of betulinic acid without disrupting its structurally related bioactivity, we have prepared different ionic derivatives of betulinic acid. Inhibition bioassays on HIV-1 protease-catalysed peptide hydrolysis indicate significantly improved performance resulting from converting the betulinic acid to organic salt form. Indeed, for one particular cholinium-based derivative, its water solubility is improved more than 100 times and the half maximal inhibitory concentration (IC50) value (22 μg mL−1) was one-third that of wide-type betulinic acid (60 μg mL−1). These encouraging results advise that additional studies of ionic betulinic acid derivatives as a therapeutic solution against HIV-1 infection are warranted.
Betulinic acid; anti-HIV; ionic liquid; HIV-1 protease; derivative
A triterpene derived from betulinic acid (RPR103611) blocks human immunodeficiency virus type 1 (HIV-1) infection and fusion of CD4+ cells with cells expressing HIV-1 envelope proteins (gp120 and gp41), suggesting an effect on virus entry. This compound did not block infection by a subtype D HIV-1 strain (NDK) or cell-cell fusion mediated by the NDK envelope proteins. The genetic basis of drug resistance was therefore addressed by testing envelope chimeras derived from NDK and a drug-sensitive HIV-1 strain (LAI, subtype B). A drug-resistant phenotype was observed for all chimeras bearing the ectodomain of NDK gp41, while the origins of gp120 and of the membrane anchor and cytoplasmic domains of gp41 had no apparent role. The envelope gene of a LAI variant, fully resistant to the antiviral effect of RPR103611, was cloned and sequenced. Its product differed from the parental sequence at two positions in gp41, with changes of arginine 22 to alanine (R22A) and isoleucine 84 to serine (I84S), the gp120 being identical. In the context of LAI gp41, the I84S substitution was sufficient for drug resistance. Therefore, in two different systems, differences in gp41 were associated with sensitivity or resistance to RPR103611. Modifications of gp41 can affect the quaternary structure of gp120 and gp41 and the accessibility of gp120 to antiviral agents such as neutralizing antibodies. However, a direct effect of RPR103611 on a gp41 target must also be envisioned, in agreement with the blocking of apparently late steps of HIV-1 entry. This compound could be a valuable tool for structure-function studies of gp41.
We have examined cross-clade HIV-specific cytotoxic T-lymphocyte (CTL) activity in peripheral blood of eight Zambian individuals infected with non-B-clade human immunodeficiency virus type 1 (HIV-1). Heteroduplex mobility assay and partial sequence analysis of env and gag genes strongly suggests that all the HIV-infected subjects were infected with clade C HIV-1. Six of eight C-clade HIV-infected individuals elicited CTL activity specific for recombinant vaccinia virus-infected autologous targets expressing HIV gag-pol-env derived from B-clade HIV-1 (IIIB). Recognition of individual recombinant HIV-1 B-clade vaccinia virus-infected targets expressing gag, pol, or env was variable among the patients tested, indicating that cross-clade CTL activity is not limited to a single HIV protein. These data demonstrate that HIV clade C-infected individuals can mount vigorous HIV clade B-reactive CTL responses.
BMS-599793 is a small molecule entry inhibitor that binds to human immunodeficiency virus type 1 (HIV-1) gp120, resulting in the inhibition of CD4-dependent entry into cells. Since BMS-599793 is currently considered a candidate microbicide drug, we evaluated its efficacy against a number of primary patient HIV isolates from different subtypes and circulating recombinant forms (CRFs) and showed that activity varied between ∼3 ρM and 7 μM at 50% effective concentrations (EC50s). Interestingly, CRF01_AE HIV-1 isolates consistently demonstrated natural resistance against this compound. Genotypic analysis of >1,600 sequences (Los Alamos HIV sequence database) indicated that a single amino acid polymorphism in Env, H375, may account for the observed BMS-599793 resistance in CRF01_AE HIV-1. Results of site-directed mutagenesis experiments confirmed this hypothesis, and in silico drug docking simulations identified a drug resistance mechanism at the molecular level. In addition, CRF01_AE viruses were shown to be resistant to multiple broadly neutralizing monoclonal antibodies. Thus, our results not only provide insight into how Env polymorphisms may contribute to entry inhibitor resistance but also may help to elucidate how HIV can evade some broadly neutralizing antibodies. Furthermore, the high frequency of H375 in CRF01_AE HIV-1, and its apparent nonoccurrence in other subtypes, could serve as a means for rapid identification of CRF01_AE infections.
Maraviroc (UK-427,857) is a selective CCR5 antagonist with potent anti-human immunodeficiency virus type 1 (HIV-1) activity and favorable pharmacological properties. Maraviroc is the product of a medicinal chemistry effort initiated following identification of an imidazopyridine CCR5 ligand from a high-throughput screen of the Pfizer compound file. Maraviroc demonstrated potent antiviral activity against all CCR5-tropic HIV-1 viruses tested, including 43 primary isolates from various clades and diverse geographic origin (geometric mean 90% inhibitory concentration of 2.0 nM). Maraviroc was active against 200 clinically derived HIV-1 envelope-recombinant pseudoviruses, 100 of which were derived from viruses resistant to existing drug classes. There was little difference in the sensitivity of the 200 viruses to maraviroc, as illustrated by the biological cutoff in this assay (= geometric mean plus two standard deviations [SD] of 1.7-fold). The mechanism of action of maraviroc was established using cell-based assays, where it blocked binding of viral envelope, gp120, to CCR5 to prevent the membrane fusion events necessary for viral entry. Maraviroc did not affect CCR5 cell surface levels or associated intracellular signaling, confirming it as a functional antagonist of CCR5. Maraviroc has no detectable in vitro cytotoxicity and is highly selective for CCR5, as confirmed against a wide range of receptors and enzymes, including the hERG ion channel (50% inhibitory concentration, >10 μM), indicating potential for an excellent clinical safety profile. Studies in preclinical in vitro and in vivo models predicted maraviroc to have human pharmacokinetics consistent with once- or twice-daily dosing following oral administration. Clinical trials are ongoing to further investigate the potential of using maraviroc for the treatment of HIV-1 infection and AIDS.
The compound 3-O-(3′,3′-dimethylsuccinyl)-betulinic acid (DSB) potently and specifically inhibits human immunodeficiency virus type 1 (HIV-1) replication by delaying the cleavage of the CA-SP1 junction in Gag, leading to impaired maturation of the viral core. In this study, we investigated HIV-1 resistance to DSB by analyzing HIV-1 mutants encoding a variety of individual amino acid substitutions in the CA-SP1 cleavage site. Three of the substitutions were lethal to HIV-1 replication owing to a deleterious effect on particle assembly. The remaining mutants exhibited a range of replication efficiencies; however, each mutant was capable of replicating in the presence of concentrations of DSB that effectively inhibited wild-type HIV-1. Mutations conferring resistance to DSB also led to impaired binding of the compound to immature HIV-1 virions and loss of DSB-mediated inhibition of cleavage of Gag. Surprisingly, two of the DSB-resistant mutants retained an intermediate ability to bind the compound, suggesting that binding of DSB to immature HIV-1 particles may not be sufficient for antiviral activity. Overall, our results indicate that Gag amino acids L363 and A364 are critical for inhibition of HIV-1 replication by DSB and suggest that these residues form key contacts with the drug in the context of the assembling HIV-1 particle. These results have implications for the design of and screening for novel inhibitors of HIV-1 maturation.
Papuamide A is representative of a class of marine derived cyclic depsipeptides, reported to have cytoprotective activity against HIV-1 in vitro. We show here that papuamide A acts as an entry inhibitor, preventing human immunodeficiency virus infection of host cells and that this inhibition is not specific to R5 or X4 tropic virus. This inhibition of viral entry was determined to not be due to papuamide A binding to CD4 or HIV gp120, the two proteins involved in the cell-virus recognition and binding. Furthermore, papuamide A was able to inhibit HIV pseudotype viruses expressing envelope glycoproteins from vesicular stomatitis virus or amphotropic murine leukemia virus indicating the mechanism of viral entry inhibition is not HIV-1 envelope glycoprotein specific. Time delayed addition studies with the pseudotyped viruses show that papuamide A inhibits viral infection only at the initial stage of the viral life cycle. Additionally, pretreatment studies revealed that the virus, and not the cell, is the target of papuamide A’s action. Together, these results suggest a direct virucidal mechanism of HIV-1 inhibition by papuamide A. We also demonstrate here that the other papuamides (B-D) are able to inhibit viral entry indicating that the free amino moiety of 2,3-diaminobutanoic acid residue is not required for the virucidal activity.
HIV; papuamide A; cyclic depsipeptide; entry inhibitor; marine metabolite
Tumor, is one of the major reason for human death, due to its widespread occurrence. Betulinic acid derivatives have attracted considerable attention as cancer chemopreventive agents and also as cancer therapeutics. Many of its derivatives inhibit the growth of human cancer cell lines by triggering apoptosis. With this background, we planned to synthesize a series of betulinic acid derivatives to assess their antiproliferation efficacy on human cancer cell lines.
A series of novel betulinic acid derivatives were designed and synthesized as highlighted by the preliminary antitumor evaluation against MGC-803, PC3, A375, Bcap-37 and A431 human cancer cell lines in vitro. The pharmacological results showed that some of the compounds displayed moderate to high levels of antitumor activities with most of new exhibiting higher inhibitory activities compared to BA. The IC50 values of compound 3c on the five cancer cell lines were 2.3, 4.6, 3.3, 3.6, and 4.3 μM, respectively. Subsequent fluorescence staining and flow cytometry analysis (FCM) indicated that compound 3c could induce apoptosis in MGC-803 and PC3 cell lines, and the apoptosis ratios reached the peak (37.38% and 33.74%) after 36 h of treatment at 10 μM.
This study suggests that most of betulinic acid derivatives could inhibit the growth of human cancer cell lines. Furthermore, compound 3c could induce apoptosis of cancer cells.
Triterpene derivatives were analyzed for anti-HIV-1 activity and for cellular toxicity. Betulinic aldehyde, betulinic nitrile, and morolic acid derivatives were identified to have anti-HIV-1 activity. These derivatives inhibit a late step in virus replication, likely virus maturation.
retrovirus; antiviral; antiretroviral; proteolysis; protease
In our continuing study of triterpene derivatives as potent anti-HIV agents, different C-3 conformationally restricted betulinic acid (BA, 1) derivatives were designed and synthesized in order to explore the conformational space of the C-3 pharmacophore. 3-O-Monomethylsuccinyl- betulinic acid (MSB) analogs were also designed to better understand the contribution of the C-3′ dimethyl group of bevirimat (2), the first-in-class HIV maturation inhibitor, which is currently in phase IIb clinical trials. In addition, another triterpene skeleton, moronic acid (MA, 3) was also employed to study the influence of the backbone and the C-3 modification towards the anti-HIV activity of this compound class. This study enabled us to better understand the structure-activity relationships (SAR) of triterpene-derived anti-HIV agents, and led to the design and synthesis of compound 12 (EC50: 0.0006 μM), which displayed slightly better activity than 2 as a HIV-1 maturation inhibitor.
3-O-(3′,3′-Dimethysuccinyl) betulinic acid (PA-457) has been shown to potently inhibit human immunodeficiency virus (HIV) replication in culture. In contrast to inhibitors that act upon the viral proteinase, PA-457 appears to block only the final maturational cleavage of p25CA-p2 to p24CA. However, attempts to replicate this effect in vitro using recombinant Gag have failed, leading to the hypothesis that activity is dependent upon the assembly state of Gag. Using a synthesis/assembly system for chimeric HIV type 1 Gag proteins, we have replicated the activity of PA-457 in vitro. The processing of assembled chimeric Gag can be inhibited by the addition of drug with only the final cleavage of p25CA-p2 to p24CA blocked. Consistent with our hypothesis and with previous findings, inhibition appears specific to Gag assembled into an immature capsid-like structure, since synthetic Gag that remains unassembled is properly processed in the presence of the compound. To further analyze the authenticity of the assay, PA-457 was tested in parallel with its inactive parental compound, betulinic acid. Betulinic acid had no effect upon p25 processing in this system. Analysis of a PA-457-resistant mutant, A1V, in this system pointed to more rapid cleavage as a possible mechanism for resistance. However, characterization of additional mutations at the cleavage site and in p2 suggests that resistance does not strictly correlate with the rate of cleavage. With the establishment of an in vitro assay for the detection of PA-457 activity, a more detailed characterization of its mechanism of action will be possible.
The HIV-1 maturation inhibitor, 3-O-(3′,3′-dimethylsuccinyl) betulinic acid (bevirimat, PA-457) is a promising drug candidate with 10 nM in vitro antiviral activity against multiple wild-type (WT) and drug-resistant HIV-1 isolates. Bevirimat has a novel mechanism of action, specifically inhibiting cleavage of spacer peptide 1 (SP1) from the C-terminus of capsid which results in defective core condensation.
Methods and Findings
Oral administration of bevirimat to HIV-1-infected SCID-hu Thy/Liv mice reduced viral RNA by >2 log10 and protected immature and mature T cells from virus-mediated depletion. This activity was observed at plasma concentrations that are achievable in humans after oral dosing, and bevirimat was active up to 3 days after inoculation with both WT HIV-1 and an AZT-resistant HIV-1 clinical isolate. Consistent with its mechanism of action, bevirimat caused a dose-dependent inhibition of capsid-SP1 cleavage in HIV-1-infected human thymocytes obtained from these mice. HIV-1 NL4-3 with an alanine-to-valine substitution at the N-terminus of SP1 (SP1/A1V), which is resistant to bevirimat in vitro, was also resistant to bevirimat treatment in the mice, and SP1/AIV had replication and thymocyte kinetics similar to that of WT NL4-3 with no evidence of fitness impairment in in vivo competition assays. Interestingly, protease inhibitor-resistant HIV-1 with impaired capsid-SP1 cleavage was hypersensitive to bevirimat in vitro with a 50% inhibitory concentration 140 times lower than for WT HIV-1.
These results support further clinical development of this first-in-class maturation inhibitor and confirm the usefulness of the SCID-hu Thy/Liv model for evaluation of in vivo antiretroviral efficacy, drug resistance, and viral fitness.
Human immunodeficiency virus type 1 (HIV-1) vaccine development requires selection of appropriate envelope (Env) immunogens. Twenty HIV-1 Env glycoproteins were examined for their ability to bind human anti-HIV-1 monoclonal antibodies (MAbs) and then used as immunogens in guinea pigs to identify promising immunogens. These included five Envs derived from chronically infected individuals, each representing one of five common clades and eight consensus Envs based on these five clades, as well as the consensus of the entire HIV-1 M group, and seven transmitted/founder (T/F) Envs from clades B and C. Sera from immunized guinea pigs were tested for neutralizing activity using 36 HIV-1 Env-pseudotyped viruses. All Envs bound to CD4 binding site, membrane-proximal, and V1/V2 MAbs with similar apparent affinities, although the T/F Envs bound with higher affinity to the MAb 17b, a CCR5 coreceptor binding site antibody. However, the various Envs differed in their ability to induce neutralizing antibodies. Consensus Envs elicited the most potent responses, but neutralized only a subset of viruses, including mostly easy-to-neutralize tier 1 and some more-difficult-to-neutralize tier 2 viruses. T/F Envs elicited fewer potent neutralizing antibodies but exhibited greater breadth than chronic or consensus Envs. Finally, chronic Envs elicited the lowest level and most limited breadth of neutralizing antibodies overall. Thus, each group of Env immunogens elicited a different antibody response profile. The complementary benefits of consensus and T/F Env immunogens raise the possibility that vaccines utilizing a combination of consensus and T/F Envs may be able to induce neutralizing responses with greater breadth and potency than single Env immunogens.
We have found that novel pyridine oxide derivatives are inhibitors of a wide range of human immunodeficiency virus (HIV) type 1 (HIV-1) and HIV-2 strains in CEM cell cultures. Some of the compounds showed inhibitory activities against recombinant HIV-1 reverse transcriptase (RT), whereas others were totally inactive against this viral protein in vitro. Partial retention of anti-HIV-1 activity against virus strains that contain a variety of mutations characteristic of those for resistance to nonnucleoside RT inhibitors and a lack of inhibitory activity against recombinant HIV-2 RT suggested that these pyridine oxide derivatives possess a mode of antiviral action independent from HIV RT inhibition. Time-of-addition experiments revealed that these pyridine oxide derivatives interact at a postintegration step in the replication cycle of HIV. Furthermore, it was shown that these compounds are active not only in acutely HIV-1-infected cells but also in chronically HIV-infected cells. A dose-dependent inhibition of virus particle release and viral protein expression was observed upon exposure to the pyridine oxide derivatives. Finally, inhibition of HIV-1 long terminal repeat-mediated green fluorescence protein expression in quantitative transactivation bioassays indicated that the additional target of action of the pyridine oxide derivatives may be located at the level of HIV gene expression.
Human immunodeficiency virus (HIV) transmission through saliva is extremely low. Several oral components, including secretory immunoglobulin A and secretory leukocyte protease inhibitor, are known as potential inhibitory agents of HIV oral transmission. Here we examined anti-HIV activity of oral bacterial components. We showed that recombinant protein HGP44 derived from Porphyromonas gingivalis, one of the primary infectious agents of periodontitis, was capable of inhibiting HIV type 1 (HIV-1) replication. HGP44 bound specifically to HIV-1 gp120 and blocked HIV-1 envelope-mediated membrane fusion. These findings suggest that HGP44 of P. gingivalis can inhibit HIV-1 infection by blocking HIV-1 entry.
We previously identified a small-molecule anti-human immunodeficiency virus type 1 (anti-HIV-1) compound, ADS-J1, using a computer-aided molecular docking technique for primary screening and a sandwich enzyme-linked immunosorbent assay (ELISA) as a secondary screening method. In the present study, we demonstrated that ADS-J1 is an HIV-1 entry inhibitor, as determined by a time-of-addition assay and an HIV-1-mediated cell fusion assay. Further mechanism studies confirmed that ADS-J1 does not block gp120-CD4 binding and exhibits a marginal interaction with the HIV-1 coreceptor CXCR4. However, ADS-J1 inhibited the fusion-active gp41 core formation mimicked by peptides derived from the viral gp41 N-terminal heptad repeat (NHR) and C-terminal heptad repeat (CHR), as determined by ELISA, native polyacrylamide gel electrophoresis, and circular dichroism analysis. Moreover, using a surface plasmon resonance assay, we found that ADS-J1 could bind directly to IQN17, a trimeric peptide containing the gp41 pocket region, resulting in the conformational change of IQN17 and the blockage of its interaction with a short D peptide, PIE7. The positively charged residue (K574) located in the gp41 pocket region is critical for the binding of ADS-J1 to NHR. These results suggest that ADS-J1 may bind to the viral gp41 NHR region through its hydrophobic and ionic interactions with the hydrophobic and positively charged resides located in the pocket region, subsequently blocking the association between the gp41 NHR and CHR regions to form the fusion-active gp41 core, thereby inhibiting HIV-1-mediated membrane fusion and virus entry.
T22, an analog of polyphemusin II (18 amino acid residues), was found to block T-tropic human immunodeficiency virus type 1 (HIV-1) entry into target cells as a CXCR4 inhibitor. We synthesized T134, a small analog (14 amino acid residues) of T22 with reduced positive charges. T134 exhibited highly potent activity and significantly less cytotoxicity in comparison to that of T22. T134 prevents the anti-CXCR4 monoclonal antibody from binding to peripheral blood mononuclear cells but has no effect on the binding of anti-CCR5 monoclonal antibodies. Since T134 inhibits the binding of stromal cell-derived factor-1 (SDF-1) to MT-4 cells, it seems that T134 prevents HIV-1 entry by binding to CXCR4. The bicyclam AMD3100 has also been shown to block HIV-1 entry via CXCR4 but not via CCR5. Both T134 and AMD3100 are CXCR4 antagonists and low-molecular-weight compounds but have different structures. Our results indicate that T134 is active against wild-type T-tropic HIV-1 strains and against AMD3100-resistant strains.
Pradimicin A (PRM-A), an antifungal nonpeptidic benzonaphtacenequinone antibiotic, is a low-molecular-weight (molecular weight, 838) carbohydrate binding agent (CBA) endowed with a selective inhibitory activity against human immunodeficiency virus (HIV). It invariably inhibits representative virus strains of a variety of HIV-1 clades with X4 and R5 tropisms at nontoxic concentrations. Time-of-addition studies revealed that PRM-A acts as a true virus entry inhibitor. PRM-A specifically interacts with HIV-1 gp120 and efficiently prevents virus transmission in cocultures of HUT-78/HIV-1 and Sup T1 cells. Upon prolonged exposure of HIV-1-infected CEM cell cultures, PRM-A drug pressure selects for mutant HIV-1 strains containing N-glycosylation site deletions in gp120 but not gp41. A relatively long exposure time to PRM-A is required before drug-resistant virus strains emerge. PRM-A has a high genetic barrier, since more than five N-glycosylation site deletions in gp120 are required to afford moderate drug resistance. Such mutated virus strains keep full sensitivity to the other known clinically used anti-HIV drugs. PRM-A represents the first prototype compound of a nonpeptidic CBA lead and, together with peptide-based lectins, belongs to a conceptually novel type of potential therapeutics for which drug pressure results in the selection of glycan deletions in the HIV gp120 envelope.
Inspired by the anti-human immunodeficiency virus (HIV) activity of analogues of β-galactosylceramide (GalCer), a set of mono- and di- saccharide fatty acid esters were designed as GalCer mimetics and their binding to the V3 loop peptide of HIV-1 and anti-HIV activity evaluated. 1,1-linked Gal-Man and Glu-Man disaccharides with an ester on the Man subunit bound the V3 loop peptide and inhibited HIV infectivity in single round infection assays with the TZM-bl cell line. IC50's were in the 50 μM range with no toxicity to the cells at concentrations up to 200 μM. These compounds appear to inhibit virus entry at early steps in viral infection since they were inactive if added post viral entry. Although these compounds were found to bind to the V3 loop peptide of gp120, it is not clear that this interaction is responsible for their anti-HIV activity because the relative binding affinity of closely related analogues did not correlate with their antiviral behavior. The low cytotoxicity of these 1,1-linked disaccharide fatty acid esters, combined with the easy accessibility to structurally diverse analogues make these molecules attractive leads for new topical anti-viral agents.
Galactosylceramide; glycolipid; trehalose; fatty acid; antiviral; HIV